The present invention relates to assembly line production of circuit boards, and more particularly, to continuous carriers for connectors adapted for soldering to surface mount technology ("SMT") circuit boards.
Conductive pins and posts have long been used for connecting leads, terminals and electronic components to conductive traces or other devices mounted on printed circuit boards ("PCBs") and in some cases, for connecting one PCB to an adjacent PCB. In recent years pins and posts have been developed for SMT applications. Pins have been provided with a base or head that is precisely placed on a solder pad by a pick and place machine. Usually multiple-pins are rapidly placed in succession on an SMT cicuit board. After solder re-flow, the upper ends of the pins can be used to attach wires, leads, devices or another PCB in parallel relationship.
Tape and reel supply of small discrete parts such as electrical and mechanical components for automatic pick and place onto a PCB, SMT circuit board or other substrate is widely used in the electronics industry. Examples of pick and place machines are those commercially available from Universal, Panasonic, Fuji and others. Typically the pick and place machines have multiple removable parallel feeders which each support a tape reel carrying a different component. An example of such a feeder is the MPF856 commercially available from Hover-Davis, Inc. In one carrier tape system commercialized by Advantek and 3M a plastic carrier tape with sprocket holes along one or both side edges is embossed to form a series of pockets which each carry a separate component covered by a continuous strip. The carrier tape is unreeled, its cover strip is peeled back, and a pick and place head removes a component from each pocket that is adapted for surface mount or through hole attachment. The component is placed under precise computer control onto a given location on a PCB. The PCB usually has solder paste applied at precise locations which temporarily holds the component in place until solder re-flow. It would be impractical to elongate the pockets sufficiently to receive pins in a vertical orientation. Furthermore, even if the pocket could be drawn deep enough, such an arrangement would not position the head of the pin accurately enough for suction pick-up by the nozzle of the pick and place machine.
The use of hoppers or bins for feeding pins to a conventional pick and place machine is undesirable because of the substantial room that they occupy, their tendency to jam, and difficulties in reliably picking up individual pins with the head of the pick and place machine. It is also not desirable to supply pins to a conventional pick and place machine in individual pockets of a continuous carrier tape due to problems in retrieving the pin in the proper orientation with the head of the pick and place machine for subsequent vertical placement on the SMT circuit board. While the AUTOPAK continuous carrier tape product is well suited for many applications, it does require that the part be over-molded with respect to at least one tape. Such over-molding is not practical with metal pins which are often cold formed. It would therefore be desirable to provide a continuous carrier for pins that would be suited for use in conventional pick and place machines which would not require that the pins be over-molded by the continuous carrier.